This invention relates to channel selecting apparatus for use with a signal receiver which is coupled to a first tuning device and with a signal recorder which is coupled to a second tuning device such that the information contained in the channel to which the first tuning device is tuned is received by the signal receiver and the information which is contained in the channel to which the second tuning device is tuned is recorded by the signal recorder, and more particularly, to channel selecting apparatus of the aformentioned nature wherein the information which is supplied by the second tuning device to the signal recorder also is supplied to the signal receiver.
In the field of signal receiving and recording, it often is desirable to record signal information which is included in one channel, such as signal information which is transmitted on one broadcast frequency, while receiving or monitoring signal information which is included in a different channel. For example, in television receiving and recording applications, it may be desirable to record on a video recorder, such as a video tape recorder (VTR), video signals which are included in one channel while displaying on a television receiver, or monitor, a video picture which is contained in a different channel. In general, this is achieved by providing separate tuning devices. Typically, the VTR is provided with one tuning device while the television receiver is provided with another tuning device, both of these tuning devices being operated independently of each other so as to receive different channels, or broadcast frequencies. Accordingly, the user may view one television program while recording a different television program.
In early embodiments of signal receivers and recorders, the respective, independent tuning devices provided therein included electromechanical tuners. More recently, it has been found that electronic tuners provide a distinct advantage over the earlier electromechanical devices. In general, an electronic tuner includes a variable reactance device, such as a varactor, or varicap diode, whose reactance is determined by a control voltage applied thereto. Such electronic tuners do not use turret-type tuning capacitors having mechanical detents, or stops, intrinsic to prior art electromechanical tuners. Consequently, the electronic tuners do not suffer from oxidized or worn contacts, difficult operation and relatively short life associated with electromechanical tuners. When such electronic tuners are used in television receivers and recorders, separate selector switches, such as pushbutton switches, may be provided in the television receiver and in the VTR. This duplication of parts results in an additional expense. However, it has been thought that such separate sets of selector switches were necessary in order to insure that the respective tuning conditions of the television receiver and the VTR could be established independently of each other. However, it has been found that two electronic tuners can be controlled substantially independently of each other so as to permit the viewing and recording of different channel information, while providing only a single set of selector switches. This is particularly advantageous when the television receiver and VTR are contained within the same housing or cabinet. One example of such channel selecting apparatus wherein a single set of selector switches is used to control the tuning conditions of two separate electrically tunable tuning devices is disclosed in copending application Ser. No. 912,080, assigned to the assignee of the present invention.
In the channel selecting apparatus of the type disclosed in the aforementioned copending application, selective operation of the single set of channel selector switches simultaneously determines the tuning conditions of the tuning devices in both the television receiver and in the VTR. Hence, both tuning devices generally are tuned to the same channel, depending upon which selector switch has been operated. However, when a recording operation is to be carried out, a recording switch is closed which locks the tuning device included in the VTR to the channel to which that tuning device had been tuned immediately prior to the initiation of the recording operation. Then, different channel selector switches can be operated so as to tune the television receiver to any different desired channel; while the tuning condition of the VTR is locked. This prevents undesired interruption in the channel information which is being recorded, yet permits the user to view any other desired program.
In the channel selecting apparatus of the type disclosed in the aforementioned application, as well as in other channel selecting apparatus which have been proposed heretofore, the output of the tuning device included in the television receiver is supplied only to the receiver signal processing circuitry, and the output of the tuning device included in the VTR is supplied only to the recorder processing circuitry. Although the video information which is being recorded can be monitored by tuning the television receiver to the same channel as that which is being recorded, the operability of the VTR tuning device is not known until after the video signals have been recorded and then subsequently reproduced. Hence, if the VTR tuning device is not tuned accurately, or if there is a malfunction therein, such possibilities will not be known until after the recording operation is completed. This may result in the recording of degraded video signals, which degradation could have been corrected if the video signals derived at the output of the VTR tuning device had been monitored prior to recording.